Method of manufacturing shrink-head casings



F. H. CHAPKN Oct. 20, 119.25v

METHOD OF MANUFACTURING SHRINK HEAD CASINGS Filed April 20, 1925 .WN W Wd@ .SMSI .OCH *LLL nu@ msm .2E w20 A w93@ Gm @Sms Patented oct. zo, 1925.-.

UNITED lSTATES 'PATENT OFFICE.

FRED H. CHAPIN, 0F CLEVELAND, OHIO.

METHOD 0F MNUFACTURING SHRINK-HEAD CASINGS.

. Application filed April 20, 1925. Serial No. 24,684.

To all lwhom it may concern:

Be it known that I, FRED I-I. CHArlN, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga 'and State of Ohio, have invente-d a certain new and useful Improvement in Methods of Manufacturing Shrink-Head Gasings, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings.

This invention relates to what are known in the art of ingot casting as feeders` sink heads, hot tops, or more properly shrinkvhead casings for ingot molds, the function of which is to delay the cooling or solidilication of the molten metal in the upper part of the solidifying ingot so that during the shrinkage of the ingot a 4pipe or shrinkage cavity is not formed in the major part lthereof and is confined to a relatively small part of the upper portion of the ingot formed withinthe shrink-head casing. This function of the casing is Well understood by those skilled in the art and is more fully described in my application for patent filed Apr. 20, 1925, No. 24,685, in which claims are made to the construction and composition of the casing made by the method herein described and claimed.

In the accompanying drawings Fig. lis` a perspective view of a shrink-head casing made in accordance with my invention; and Figs. 2 to 9 inclusive indicate-the various successive steps employed in the manufacture of such casings.

Ordinarily heretofore shrink-head casings have been made of refractory material such as fire clay or lire brick material which is extremely hard and brittle, having been baked at Va very high temperature and having a texture which is quite close. In order 'to make such casings, special plants have been required; it has notbeen the practice to make such casings at steel plants. Thus transportation of the casings has been necessary and the expense is correspondingly increased. When in use, the lfire clay or lirebrick casings have been supported on the 1molds by some means which allow them to descend into'the mold cavity as the ingot shrinks and solidifies. This has been found necessary as the casing adheres to the topof the ingot and, unless it is/allovvedA to lower with the shrinking ingot, it will be broken and prematurely destroyed. Then the casting operation is finished, the casing remains on top of the ingot and is usually broken up by hammers or othei` suitable tools and thus removed from the ingot before the latter is reheated and passed to the rolls for reducing the ingot to the desired shape. Quite frequently, lumps and finer particles of clay remain on the ingot and become embedded therein while passing through the rolls, thus making Haws in the rolled product which are sometimes serious.

Shrink-head casings made of fire clay have rather low heat-insulating qualities, necessitating the loss of a considerable quantity of metal from the top of the ingot where the pipe or cavity occurs, it being necessary to remove or crop this portion of the ingot after 'it 4and the vsound portionV thereof are rolled into blooms, billets, and other shapes.

It is the object of my invention toovercome the defects ordinarlly found in shrinkhead casings as heretobefore made, and I have devised a wayof making such casings of material which is not only much cheaper than fire-clay or similar refractory material, but which will produce casings of greater efficiency because possessing characteristics v which entirely eliminate some of the diiiculties heretobefore encountered in the use of clay, casings.

I have found that if blast furnace slag is properly prepared and mixed in ordinary cold water in proper proportions with commercial Portland cement, it may be molded into proper shape for use as shrinkfhead casings and that, if the surface of such a casing be treated with a suitable substance, it will casing Which Would result in what is known in the art as a boil, or such a disturbance in the forming ingot as to impede or marl the proper lcasting of the ingot, and the formation of gases in the casing which would crack or break it.

The particular shape of the casingyso far as thev present invention is concerned, is,l not essential. Various shapes may be used, but that illustrated in Fig. 1 of the drawingslis preferred. As shown, the casing B is generally rectangular in horizontal Vcross section. The lower part of the casing is rounded at the four corners, avsindilos Vcated at a., thus producingra lo\ver part b sible to obtain casings in quantity produc-l tion of uniform density or porosity, as some of the casmgs are invariably burnt l* at a higher temperature than-others in the same lot or kiln; and this baking has been performed in a special plant remote from the steel plant. The casings made in accordance'with my invention are made of relatively low-refractory material, baked or hardened at aA relatively low temperature, and may be made at the steel plant, inasmuch as I employ furnace slag as a principal ingredient of the Casing and combine such slag with a suitable proportion of commercial Portland cement, which'is readily obtainable. Blast furnace slag gives the best results, although open hearth or other slag may be used.

In the manufacture of shrink-head casings according to my invention, ordinary furnace slag taken from the dump is ground or crushed by suitable machinery until it y is in proper condition to be screened. The icrushed or ground slag 1s then screened` 1n preferably a screen of, 1/4 inch mesh.'

In this Way the larger lumps are separated from the dust and smaller particles. Y

rI'he screened slag is then thoroughly, mixed and blended with Portland cement in a suitable mixer and While dry. Pref erably one'part of the cement is mixed with seven parts oflslag by Weight, as these proportions are found to give the best results, although they may be varied. After being thoroughly mixed and blended, a

sufficient amount of ordinary cold Water may be added to the blended material While they arein the same mixer, or the blended dry cement and slag may be transferred to another container' where Water is added and the ingredients thoroughlyv kneaded .and mlxed until a mass of desired consistency for molding is produced. The material is then in condition to beI molded andv suitable moldsmay be used for this purpose, the material being packed in the molds and rammed or tamped in the usual Way until the desired shape is obtained.

The next step in the process is to re move the free imoisture from the casings, and this is done by heating the casngs for about l2 hours in what is called Va prekrendered porous and is in r`good condition to receive the impregnating liquid or substance Which serves to render inactive the gas producing constituents of the material of which the casing is made and to thus prevent the formation and liberation of gases from the casing when the latter is subjected to the intense heat of the ingot while being formed. For this purpose I preferably employ a substance sold as .Goulac, Well known to foundry men and which consists mainly of organic matter (cellulose) With the following additional ingredients Y Aluminum oxide (A1203).

Fei-ric oxide (Fe203).

Manganese oxide (MngOz).

Calcium oxide (CaO).

luagnesium oxide (MgQ).

Sulphur (S).

The cellulose in the Goulac is that obtained from the dried liquor from the manufacture of sulphite pulp. A non-organic compound such asimagnesium luosilicate lnay also be used instead of Goulae The impregnating substance may be applied by spraying, brushing, or by dipping the casing into a bath of the liquid whereby all the Walls are impregnated to a suitable distance with the impregnating substance. IVhile good resultshave been obtained where the impregnation extends from l/S to 3A inch into the casing Walls, itis preferable to impregnate the casings completely, as indicated by the stippling'at X in Fig. l. The impregnating material serves to render inactive the gas producing constituents of the material of which the casing is made as above stated, and also renders the casing as a Whole substantially water-proof so that it will .not absorb moisture 'and thus render the porous casing liable to rupture through the formation of steam thereu'ithin.

After being thus treated, the casings arc Vbaked in a suitable furnace for about l2 hours, the latter being heated to a temperature of from 600D to 800o F. which, it will be observed, is not only a much lower temperature than that employed for burning fire'clay,`but one AWhich Will not fuse the slag ingredients of the casings. V'Vhen thus baked, the casings are-complete and ready for use on the molds.

The time occupied in the preheating or preliminary heating and the nal heating the first heating to drive off the moisture in the form of steam and in the second case to dry and harden the surface of the casing where the water-proofing or impregnatiiig substance is conta-ined. As pointed out hereinbefore, about 12 liouis will be suiicient for each of these heating operations.

'liile I prefer to apply the impregnating substance to the entire exterior of each casing, it may be applied only kto the inner walls thereof which come in Contact with the molten metal of the forming ingot, and I' may apply other forms of water-proofing materialto other parts 0f the casing. lnasmuch as the interior of eachvcasing is porous and substantially moisture-free, it serves as a heat insulator, andthe metal of the forming ingot at the top of the mold is maintained in liquid condition until the formation of the ingot is completed.

` As explained in my application for patent 'above referred to, while my casing is in use the hot molten metal which rises in it when the mold is being poured softensthe inner walls of the casing, due to the fusion of the slag content thereof, and renders them nonadherent tothe ingot, so that asthe forming ingot shrinks it will draw away from the casingV without imparting harmful strains thereto. The substance with which the casing is treated prevents the swelling or spaivling of the slag constituent of the cas'- ing and thus enables the ingot to free itself from the inner walls of the casing during the solidification and shrinkage thereof.`

My invention while especially designed for use in connection with Amolds for 'forming steel ingots, may be employed in connection with molds of other kinds or molds for forming other kinds of castings. While slags and refractories of various chemical compositions will produce articles having the advantages referred to, the. best results I have found by many experiments are ob- 'tained by using a blast furnace slag containing a substantial proportion of mag# nesia. It has been stated that the plant for mak-` ing the casings is conveniently located at the steel plant where the slag is found, but it is of course feasible to make the casings in plants remote from the steel plants, al-

though this involves transportation and additional expense. In any event, by using a waste product such as slag in connection with a relatively small percentage of cement or other binding material, my casings may be made very much more cheaply than can those made of fire clay; and such casings made in accordance with my invention possess thebenefical characteristics set forth hereinbefore. which are not found in casings heretofore employed.

This application is a continuation in part of my application No. 738,774 filed September 20, 1924 and of my application No. 758,594 filed December 29, 1921.

Having thus described myA invention, what I claim is:

l.` In the manufacture of shrink head casings for ingot molds, the method herein described 'ivhich consists in mixing furnace sla-g and a binder in proportions of about 7 parts vby weight of slag to one part by weight of the binder, molding the mixture to give it the desired shape and then baking the molded article at a temperature ofv between 200o and 250 F. to removemoisture therefrom and render the casing porous'.

2. In the manufacture of shrink head casings for ingot molds, the method herein described which consists in mixing blast furnace slag and cement in proportions of about 7 parts by weight of slag to l partby weight of cement in Water, molding the mixture to give it the desired shape, and' then baking the molded article at atempeia-v ture of between 200o and 250 F. to remove moisture therefrom and render the casing porous.

3. The method herein described of making shrink hea'd casings for ingot molds which consists in mixing refractory material and a binder in water, molding this mixture, removing moisture from the molded article, and then treating the casing with a substance which renders inactive the gas forming constituents contained in the casing.

4. The method herein described which consists in mixing refractory material and a binder in water, molding this mixture, baking the molded article to remove moisture therefrom, treating the molded article with a substance which render inactive the gas forming constituents in the casing, and finally baking the casing at a relatively `high temperature but below the fusing point cement in Water, molding this mixture to.

give it the desired form, baking the molded article to remove moisture therefrom and to render the casing porous and absorbant, treating the -casing with a substance which renders inactive the gas forming constituents of the ingredients of which the casing is made, and finallybaking the casing at a relatively high temperature nbut below the fusingvpoint of the slag constituent thereof.

6. The herein described lmethod of making shrink head casingsl for ingot molds which consists in mixing refractory material and a binder in water, molding the mixture to give the desired form thereto, baking the molded article at a low temperature to drive out the moisture from the casing and render it porous and absorbent,

applying a substance to the inner Wall of the casing which serves to render inactive the gas forming constituents therein, `and vthen baking the casing at a relatively high temperature to harden it.

7 The method of manufacturing a shrink head casing for an ingot mold which consists in mixing binding material with refractory material which is fusible at the 1&1 temperature of the molten metal of an ingot,

\molding the mixture to give it the desired shape, heating the molded article thus formed to dry the same Without fusion thereof, treating the metal contacting portions of the casing with a substance which renders inactive the gas forming constituents in the casing and then baking the casing at a relatively high temperature but lower than the fusing point. Y

8; The method herein described of mak- Maase? ing shrink head casings for ingot vmolds which consists in forming a porous moisture free casing from furnace slag and a binder, impregnating such casing with a substance which renders inactive the gas forming constituents of the casing, and then baking the impregnated casing at a temperature below the fusing point of the slag.

9. In the manufacture of shrink head casings for ingot molds, the method herein described which consists in molding refractory material While in a plastic condition to give it the desired shape, and in treating the refractory material from which the casing is formed with a substance which renders inactive the gas forming constitu-- ent of the material.

In testimony whereof, I hereunto affix my* signature.

FRED H. cHAPiN. 

